tailscale/util/multierr/multierr.go

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// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package multierr provides a simple multiple-error type.
// It was inspired by github.com/go-multierror/multierror.
package multierr
import (
"errors"
"strings"
)
// An Error represents multiple errors.
type Error struct {
errs []error
}
// Error implements the error interface.
func (e Error) Error() string {
s := new(strings.Builder)
s.WriteString("multiple errors:")
for _, err := range e.errs {
s.WriteString("\n\t")
s.WriteString(err.Error())
}
return s.String()
}
// Errors returns a slice containing all errors in e.
func (e Error) Errors() []error {
return append(e.errs[:0:0], e.errs...)
}
// New returns an error composed from errs.
// Some errors in errs get special treatment:
// * nil errors are discarded
// * errors of type Error are expanded into the top level
// If the resulting slice has length 0, New returns nil.
// If the resulting slice has length 1, New returns that error.
// If the resulting slice has length > 1, New returns that slice as an Error.
func New(errs ...error) error {
dst := make([]error, 0, len(errs))
for _, e := range errs {
switch e := e.(type) {
case nil:
continue
case Error:
dst = append(dst, e.errs...)
default:
dst = append(dst, e)
}
}
// dst has been filtered and splatted.
switch len(dst) {
case 0:
return nil
case 1:
return dst[0]
}
// Zero any remaining elements of dst left over from errs, for GC.
tail := dst[len(dst):cap(dst)]
for i := range tail {
tail[i] = nil
}
return Error{errs: dst}
}
// Is reports whether any error in e matches target.
func (e Error) Is(target error) bool {
for _, err := range e.errs {
if errors.Is(err, target) {
return true
}
}
return false
}
// As finds the first error in e that matches target, and if any is found,
// sets target to that error value and returns true. Otherwise, it returns false.
func (e Error) As(target interface{}) bool {
for _, err := range e.errs {
if ok := errors.As(err, target); ok {
return true
}
}
return false
}